1. Field of the Invention
The present invention relates to an earphone, and is more particularly directed to a compact earphone assembly having an electroacoustic transducer element for transducing an electric signal derived from an audio device into sound, the earphone being directly fit in an auricle of a person to allow the person to listen to the sound.
2. Description of the Prior Art
In recent years, there has been increasingly used a compact light-weight earphone to be fit in a cavity of an auricle instead of a type to be inserted into an external auditory meatus or of a headphone type provided with a headband. Furthermore, in company with the popularization of portable audio devices, there is a growing demand for making portable audio devices light in weight and improving their attachability.
The following describes an example of a conventional earphone with reference to FIGS. 6A and 6B.
FIG. 6A shows a schematic external view of the conventional earphone, while FIG. 6B shows a view of the conventional earphone when fit in the human auricle. In FIGS. 6A and 6B, a housing body 1 incorporates an electroacoustic transducer element, and a front cap member 2 covers the front surface of the electroacoustic transducer element. A connection cord 3 is guided through a cord supporting member 4 from the housing body 1 to the outside to supply electric power from an audio apparatus to the electroacoustic transducer element. An outer casing 5 is of a substantially elliptical shape, has a major diameter L1 and a minor diameter L2, and is generically comprised of the housing body 1 and the front cap member 2. Reference numerals 6, 7, 8, and 9 respectively denote the external auditory meatus, tragus, antitragus, and auricle of a person.
The peripheral portion of the front surface of the outer casing 5 has an oval configuration. The reason why the front surface has an oval configuration is that an outer diameter of 17.4 mm is required for internally storing the electroacoustic transducer element when a circular configuration is adopted for the front surface, which results in an increased pressure to be applied to users. Therefore, an oval shape is adopted in order for the front surface portion to have a minimized size. Such an earphone is fit in the cavity of the auricle 9 so that the earphone can be retained in the ear, with the consequence that the cord supporting member 4 is caught between the tragus 7 and the antitragus 8 and that the outer casing 5 is put in contact with both a portion of the tragus 7 on the side of the external auditory meatus 6 and the cavity of the auricle 9.
However, since the conventional earphone as described above has a fixed configuration (particularly the dimensions L1 and L2 shown in FIG. 6 A are fixed), there has been a problem in that the earphone tends to easily fall out when used by a person who has a large auricle, while the earphone gives excessive pain to or cannot be fit in the ear of a person who has a small auricle.